Absolute position detection

ABSTRACT

A system for determining the absolute position of a first object with respect to a second object includes a scalar element attached to the first object and a measuring device attached to the second object. The scalar element comprises a series of coded regions. The coded region represents a number designating a position along an axis of the scalar element. The measuring device includes a two-dimensional optical sensor array configured to capture an image of a portion of the scalar element. The system also includes a processor configured to receive the image and determine an absolute position of the first object with respect to the second object based on at least one coded region of the series of coded regions.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.15/884,171, filed Jan. 30, 2018, which is a Continuation of U.S. patentapplication Ser. No. 13/918,704, filed Jun. 14, 2013, which claims thebenefit under 35 USC 119(e) of prior copending U.S. Provisional PatentApplication No. 61/678,581, filed Aug. 1, 2012, and prior copending U.S.Provisional Patent Application No. 61/660,614, filed Jun. 15, 2012, eachwhich is hereby incorporated by reference in their entirety.

BACKGROUND 1. Field

The present disclosure relates generally to determining absoluteposition along an axis of motion, and more specifically to viewing anoptically readable scalar element with a two-dimensional sensor arrayand determining an absolute position along the axis of motion.

2. Description of Related Art

Relative distance along an axis can be measured using a traditionaloptical scale. A traditional optical scale may include a series ofregularly repeating index marks set apart by a pitch that is a knowndistance. A relative distance or the position of an object along thescale can be determined by counting the number of index marks andmultiplying the count by the known distance of the pitch.

A traditional optical scale can be used to measure the relative motionbetween two objects. For example, a traditional optical scale may beattached to a first object in a location that can be viewed with respectto a reference point or indicator on a second object. The position ofthe second object can be measured with respect to the reference point bycounting the number of index marks that pass the reference point. Usingthis technique, the position along an axis can be measured bydetermining an absolute home location, usually at one end of the scale,and then counting the number of index marks from the home location. Theindex count can be stored in computer memory and incremented ordecremented depending on the movement of the second object.

One disadvantage to using a traditional scale is that the position ofthe second object cannot be determined if the index count is lost oraccumulates errors. For example, if the index count is lost due to anelectrical reset or loss of power, the position of the second objectcannot be determined without returning to the home location. Similarly,the index count may be lost if the second object is removed from thefirst object and returned in a different position along the axis.Because the index count was not incremented or decremented while thesecond object was removed, the relative position of the second objectstored in computer memory is no longer correct. Additionally, errors inthe index count can accumulate over time and result in a reportedposition that is inaccurate.

What is needed is a technique for determining absolute position along anaxis of motion without the disadvantages of a traditional optical scale.

BRIEF SUMMARY

The embodiments described herein include a measurement system formeasuring the absolute position of a first object with respect to asecond object along an axis of motion. The system comprises a scalarelement attached to the first object. The scalar element comprises aseries of coded regions, each coded region of the series of codedregions having information encoded along a direction perpendicular tothe axis of motion. The coded region represents a number designating aposition along an axis of the scalar element. A measuring device isattached to the second object and includes a two-dimensional opticalsensor array configured to capture an image of a portion of the scalarelement. A processor is configured to receive the image and determine anabsolute position of the first object with respect to the second objectbased on one coded region of the series of coded regions. In someembodiments, the two-dimensional optical sensor array is a camerasensor.

In some embodiments, each coded region of the series of coded regions isa binary code that represents a number designating a position along anaxis of the scalar element. In some embodiments, the system alsoincludes a display configured to display the absolute position to auser. The system may also include a motion controller configured toreceive the absolute position, and to cause a movement of the firstobject along the axis of motion based on the received absolute position.

In some embodiments, the measuring device is configured to capture aplurality of images as the first or second object move along the axis ofmotion and the processor is configured to determine, in real time, anabsolute position for each of the plurality of images.

In some embodiments, each coded region comprises a colored region, andthe processor is further configured to determine an absolute position ofthe first object with respect to the second object based on the coloredregion. In some cases, each coded region comprises more than one coloredregions, and the processor is further configured to determine anabsolute position of the first object with respect to the second objectbased on the more than one colored region.

The embodiments described herein include a measurement system formeasuring the absolute position of a first object with respect to asecond object. The system comprises a scalar element attached to thefirst object and a measuring device attached to the second object. Inone embodiment, the scalar element comprises a series of regularlyrepeating optically readable index lines, and a series of coded regions,each coded region of the series of coded regions disposed between twoindex lines of the series of index lines. The coded region represents anumber designating a position along an axis of the scalar element. Inanother embodiment, only the coded regions are provided.

The measuring device includes a two-dimensional optical sensor arrayconfigured to capture an image of a portion of the scalar element. Thesystem also includes a processor configured to receive the image anddetermine an absolute position of the first object with respect to thesecond object. In one embodiment, the position is based on at least oneindex line of the series of index lines and at least one coded region ofthe series of coded regions. Where only coded regions are provided, theposition is based on an image of a coded region.

DESCRIPTION OF THE FIGURES

FIG. 1 depicts a system for determining an absolute position.

FIG. 2 depicts an exemplary embodiment of a scalar element.

FIGS. 3A-C depicts portions of a scalar element.

FIGS. 4A-C depict exemplary images of portions of a scalar element.

FIG. 5 depicts another exemplary embodiment of a scalar element.

FIG. 6 depicts a method for determining absolute position rising ameasuring device and a scalar element.

FIG. 7 depicts exemplary dimensions of a scalar element.

FIG. 8 depicts an exemplary caliper.

FIG. 9 depicts a table showing an exemplary binary coding scheme using agraphical representation of binary numbers in a sequence

DETAILED DESCRIPTION

The following description is presented to enable a person of ordinaryskill in the art to make and use the various embodiments. Descriptionsof specific devices, techniques, and applications are provided only asexamples. Various modifications to the examples described herein will bereadily apparent to those of ordinary skill in the art, and the generalprinciples defined herein may be applied to other examples andapplications without departing from the spirit and scope of the variousembodiments. Thus, the various embodiments are not intended to belimited to the examples described herein and shown, but are to beaccorded the scope consistent with the claims.

The following embodiments relate to the measurement of an absoluteposition between two objects that are capable of moving with respect toeach other, at least with respect to one axis. One object may be fixedwith respect to ground and the other object may move along an axis ofmotion. The objects may be moved manually or may be driven by motor orother electromechanical device.

One exemplary embodiment is depicted in the measurement system ofFIG. 1. The measurement system 100 includes a first object 102 and asecond object 104. In the present embodiment, the first object 102 isfixed with respect to ground and the second object 104 is able to movealong the an axis (the x-axis). The second object 104 may be constrainedby a rail or mechanical guide attached to a third object 106, which isfixed with respect to ground. The range of motion of the second object104 may be limited by hard stops on either end of the third object 106.

A scalar element 110 is attached to the top face of the first object102. An exemplary scalar element 110 is described in more detail belowwith respect to FIG. 2. A measuring device 120 is attached to the bottomface of the second object 104 and disposed above the scalar element 110.In the present embodiment, the measuring device 120 remains disposedover the scalar element 110 throughout the range of motion of the secondobject 104.

The measuring device 120 includes a two-dimensional optical sensor array122. for capturing an image of a portion of the scalar element 110.Specifically, the optical sensor array 122 has an optical field of viewthat is sufficiently wide to view one or more optical features of thescalar element 110. In the present embodiment, the optical sensor array122 is a charge-coupled device (CCD) capable of producing an electricalsignal in response to light incident to the surface of the CCD. Themeasuring device 120 may include one or more optical elements (e.g.lenses) for focusing light onto the CCD. The measuring device 120 mayalso include one or more lighting elements 124 for illuminating thesurface of the scalar element 110. For example, the lighting elements124 may include one or more light emitting diodes (LEDS) configured toemit an illuminating light over the portion of the scalar element 110.The measuring device 120 is a capable of producing an image of a portionof the scalar element 110 and output the image as an array of pixelvalues.

The measuring device 120 may also include or be operatively coupled toone or more processors for interpreting the array of pixel values anddetermining an absolute position of the second object 104 with respectto the first object 102. A more detailed discussion of the imageprocessing technique is provided below with respect to process 1000depicted in FIG. 6.

FIG. 2 depicts a top view of an exemplary scalar element 110. The scalarelement 110 includes a series of regularly repeating optically readableindex lines 112. In the present embodiment, the index lines 112 arevertical lines spaced at a 0.7 mm pitch. The scalar element 110 alsoincludes a series of coded regions 114 disposed between each pair ofindex lines 112. In the present embodiment, the coded region 114includes a binary code 116, which represents a number value designatingan absolute position of the binary region with respect to the scalarelement 110.

In one embodiment, the each binary code 116 represents a valuedesignating the number of units of a known distance (or number of indexlines 112 having a known spacing) from a home location on the scalarelement 110. In FIG. 2, the home location is represented by the indexline labeled 0%. Starting from the left, the first coded region includesa binary code representing the number value 0, indicating the startinglocation or home position. The next coded region to the right of thefirst coded region includes a binary code representing the number value1, indicating that this location is spaced from the home position by oneknown distance unit. Similarly, each coded region 114 of the series ofcoded regions includes a binary code 116 representing a value thatindicates the number of units of a known distance (or the number ofindex lines 112 having a known spacing) between the coded region 114 andthe home location.

The embodiment depicted in FIG. 2 is exemplary and other techniquescould be used to designate a number value within the coded regions. Forexample, in an alternative embodiment, the coded regions could include ashaded region having a grey scale value or color value that represents anumber value indicating the number of units of distance from aparticular location on the scalar element 110. In another alternativeembodiment, the coded region could include a both a binary code and agrey scale value or color value that represents a number value. Thecoded region may also include other information, such as errorcorrection bits or optical reference marks used to register an image.

Since the binary code 116 can be used to represent a number of units ofdistance from the origin, the system does not require index lines 112.In practice, index lines are preferable since they provide a simple wayof extending the length of the scale by a factor of two. Also, the indexlines have a high contrast that can be more easily measured. It shouldbe noted that the extended length index lines depicted in FIG. 2(corresponding to the numbers 0, 10, 20, 30, and 40) are not requiredand are used to aid human observation.

Note also that it is possible that the binary code 116 can be arrangedto correspond to an actual, absolute total distance from the originrather than a unit distance multiplier.

In FIG. 2, the pattern on the scalar element is arranged along astraight line and attached to a flat surface. In alternativeembodiments, the pattern on the scalar element could be arranged along acurve and the scalar element could be attached to an arced, helical, orother topographically shaped surface.

As discussed above, the measuring device 120 includes a two-dimensionaloptical sensor array configured to capture an image of a portion of thescalar element 110. With respect to the present embodiment, thetwo-dimensional optical sensor array is a black and white CCD camerasensor coupled with an optical element configured to produce an imagerepresenting an approximately 0.7 mm square portion of the scalarelement 110.

FIGS. 3A-C depict exemplary portions of a scalar element as viewed bythe measuring device. FIGS. 3A-C represent an exemplary optical field ofview, which is typically larger than the side of the image produced bythe camera sensor. FIGS. 4A-C depict images of the portion of the scalarelement produced by the measuring device. The images depicted in FIGS.4A-C correspond to the portions of the scalar element depicted in FIGS.3A-C.

As shown in FIGS. 3A-C, the optical field of view of the measuringdevice 120 is sufficiently large to view at least index line 112 and atleast one coded region 114 having a binary code 116. Accordingly, asshown in FIGS. 4A-C, the field of view of the measuring device 120 issufficiently large to produce an image having pixel data for least oneindex line 112 and at least one coded region 114 (including binary code116) regardless of the position of the measuring device 120 with respectto the scalar element 110. In some embodiments, the image is larger andincludes three features of the scalar element 110: one index line 112,one coded region 114, and one more feature that is either an index line112 or a coded region 114. In embodiments that do not include indexlines, only the binary code 116 portion of the coded region 114 need becaptured in the image.

As shown in FIGS. 4A-C, an image produced by the measuring device 120 iscomposed of a two-dimensional array of pixels. As explained in moredetail below with respect to process 1000, image processing may beperformed on the image to improve the quality of the pixel data. Forexample, a threshold filter or other image processing technique may beapplied to the acquired image to convert the image into an array ofblack and white (on or off) pixel data. Further processing may beperformed to group pixels that represent a feature on the scalar element110 and to determine the position of the pixel groups within the image.

Within the image, the position information of the pixel groups can beused to improve the precision of the position of the measuring device120 with respect to the scalar element 110. For example, as shown inFIGS. 4A-C, the center of a pixel group 404 can be determined byaveraging the location of pixels within the group along an axis of theimage. The center of the image 406 can also be determined. Using thecenter of the pixel group 404 and the center of the image 406, an offset406 between the coded region and the optical center of the measuringdevice 120 can be determined. The offset 406 can then be added orsubtracted from the absolute position indicated by the coded region toimprove the precision of the measurement. The same technique can beapplied to pixel groups that represent a coded region and pixel groupsthat represent an index line.

In the present embodiment, the index lines 112 have a width ofapproximately 0.1 mm and are spaced approximately 0.7 mm apart. Thebinary code 116 includes binary elements that are approximately 0.1 mmwide and are also spaced approximately 0.7 mm apart. The binary elementsof the binary code are arranged along a direction that is perpendicularto the axis of motion between the scalar element 110 and the measuringdevice 120. More generally, the coded region typically includesinformation that is encoded along a direction perpendicular to the axisof motion. In the present embodiment, the information is encoded onlyalong a direction that is perpendicular to the axis of motion.

FIG. 7 depicts other exemplary dimensions for an exemplary scalarelement 710. A full view of the scalar element 510 is depicted on theleft hand of FIG. 7 and indicates a 70 mm working length of the scalarelement 510 that include index lines 512 and coded regions 514. The twodetail views (Detail A and Detail B) depict left and right portions ofthe scalar element 510, respectively. As shown in FIG. 7, the index line512 is 1 mm long and the coded region is 0.8 mm long.

With respect to FIGS. 2, 3A-C, and 7, the position of the binaryelements within the coded region represents the bit location within an 8bit word. The color of the binary element represents the bit value (0or 1) for the corresponding bit location. For example, the top or firstlocation represents first bit in the word. A binary element in the firstlocation indicates a binary value of 1 for the first bit and a binaryelement in the second element represents a binary value of 1 for thesecond bit and so on. FIG. 9 depicts a table showing an exemplary binarycoding scheme using a graphical representation of binary numbers in asequence. The example in FIG. 9 uses a graphical binary element placedin one of 8 locations to create an 8-bit coding scheme. Additional bitscould be accommodated by expanding the number of locations or by usingcolor-coded elements, as described in more detail below with respect toFIG. 5.

As described in more detail below with respect to process 1000, theindex lines and the coded regions can both be used to determine anabsolute position along the scalar element. Specifically, the codedregion represents a number value indicating the number of index linesfrom a known location on the scalar element. As previously mentioned,the position of the index lines within the image allows the system todetermine a precise position of the measuring device with respect to thescalar element by indicating the relative location of the coded regionwithin the image. Combining the information provided by the coded regionwith the information provided by the location of the index lines, thesystem can determine the absolute position of the measuring device withrespect to the scalar element. As noted above, in some embodiments, theabsolute position can be determined using only the coded region withoutreference to index lines.

The coded region and the index lines can also be used together toproduce rapid position feedback between the first and second objects.For example, the index lines can be used to count the number of stepsduring a rapid motion between the two objects. The count of the numberof index lines can be used to determine the magnitude of the rapidmotion and can be used as position feedback for a motion control system,for example. The coded region can then be used near the end or at theend of the movement to verify or correct the magnitude of the rapidmotion and provide an absolute position of the second object withrespect to the first object.

By having the coding regions encoded with information along a directionthat is perpendicular to the axis of motion, additional advantages maybe utilized. Specifically, the coded regions can be used to count thenumber of steps as described above with respect to the index lines.Accordingly, the coded region can serve a dual role as both an indicatorfor counting relative motion and as a representation of the absolutelocation.

In an alternative embodiment, the measuring device may include a colorcamera sensor and the scalar element may include one or more color-codedregions that provides additional information about the location of thecoded regions with respect to a known location on the scalar element.FIG. 5 depicts another exemplary scalar element 510. As shown in FIG. 5,the scalar element 510 includes a color-coded region 118 that, togetherwith other portions of the coded regions 114, represents a numberindicating the number of index lines from a known location on the scalarelement. For example, the color of the color-coded region 118 mayindicate an additional bit of information used to determine the numberrepresented by the coded regions 114.

The location of the color-coded regions 118 may provide additionalinformation used to determine the distance from the home position. Forexample, the position of the color-coded region 118 may designateadditional bits of information that can be used to determine the numberof units of distance from the home position. The color-coded region maybe a portion of the coded region or the entire background color of thecoded region, or both.

In the embodiment of FIG. 5, the color coded region 118 is aligned withthe first binary bit. One can obtain a full extra eight bits ofinformation by moving the region around, adding regions and/or expandingthe region. In this regard, the color regions could be laid out in muchthe same way as the bits are shown in the table in FIG. 9. For example,decimal 5 would include color strips aligned with the locationcorresponding to the first and third binary bits, while decimal 7 couldinclude a broad color strip aligned with the location corresponding tothe first three binary bits.

The above concept can be expanded to include stripes having differentcolors, such as red, blue, and green. One advantage of using multiplecolor-coded regions is that the amount of information that can beencoded in the coded region can be significantly expanded. For example,if an n-number of colors are used, the color region can be used torepresent n-based number sequences. In this way, the color and locationof the one or more color-coded regions can be used to expand the amountof information contained on the scalar element 110 without increasingthe width of the scalar element or the field of view of the measuringdevice 120.

The features described with respect to the measuring device 120 and thescalar element 110 can be used in various combinations to achieve anabsolute position of a first object with respect to a second object. Inaddition, the particular configuration may vary without departing fromthe nature of the measurement system 100. For example, the scalarelement 110 may be attached to the second object 104 and the measurementdevice 104 may be attached to the first object.

There are multiple implementations of the measuring system describedwith respect to the embodiments described above that can be used todetermine the absolute position of a first object with respect to asecond object. For example, the first object may include a base stageelement in a gantry robot system. The second object may include amovable armature that is able to traverse with respect to the base stageelement. Accordingly, a measurement system in accordance with theembodiments herein can be used to determine an absolute position of thearmature with respect to the base stage element. The gantry robot systemmay include motion controller electronics for controlling motors formoving the armature. The motion controller electronics may use theabsolute position of the armature as position feedback for controllingthe motion and positioning the armature. As described below with respectto process 1000, the measurement system can be used to calculate anabsolute position in real time as the measuring device (or scalarelement) is moved, which is advantageous in providing rapid and accurateposition feedback to motion controller electronics.

Another exemplary embodiment is described with respect to a bottledispenser with a digital volume display. A description of a bottledispenser embodiment is attached as Appendix A and incorporated byreference herein in its entirety. Another description of a bottledispenser embodiment is attached as Appendix B and incorporated byreference herein in its entirety. A description of the bottle dispenserembodiment is also provided in published application WO/2012/103870which is incorporated by reference herein in its entirety. In theseembodiments, the distance measured by the system is converted into avolume of dispensed fluid.

FIG. 6 depicts a flow chart for an exemplary process 1000 fordetermining absolute position using a measuring device and a scalarelement. The process 1000 may be implemented as computer-readableinstruction executed on one or more computer processors.

In operation 1002, an image is acquired using the measuring device. Asdescribed above with respect to FIGS. 4A-C, the measuring device 120 canbe used to produce an image of a portion of the scalar element 110. Theimage includes at least one coded region 114. In some embodiments theimage includes at least one index line 112 and at least one coded region114.

In operation 1004, image processing is performed on the acquired image.For example, a threshold filter or other image processing technique maybe applied to the acquired image to convert the image data to binaryvalues for each pixel in the image. Additional image processing may beperformed to determine pixel groups and the shape and location of thepixel groups within the image. The location of the pixel groups may berepresentative of the location of the index lines and the coded regionsof the scalar element with respect to the measuring device.

In operation 1006, the pixel groups of the image representing one ormore coded regions is used to determine a number value. As discussedabove with respect to FIG. 2, the value may indicate the number of unitsof distance (or number of index lines of known spacing) from a known orhome position on the scalar element. In one example, the coded regionincludes a binary code having binary elements that are position withinthe coded region. The number and position of the binary elements can beused to determine the number value.

In operation 1008, an offset of the coded region is determined withinthe image. As shown in FIGS. 4A-C, the position of the coded region mayvary within the captured image. In one example, one or more pixel groupsin the image may represent one or more index lines and can be used todetermine the center of the pixel group representing the coded regionwithin the image. This position information can be used, for example, todetermine an offset between the center of the coded region and thecenter of the image.

In operation 1010, an absolute position is determined using the numberand the position of the coded region within the image. For example, thevalue may represent the number of units of distance (or the number ofindex lines of known spacing) from a known position along the scalarelement. By multiplying the number of units times the known distance orspacing between coded regions, an absolute position of measuring devicecan be determined. The accuracy of the absolute position can then beimproved by, for example, adding (or subtracting) the offset between thecenter of the coded region and the center of the image determined inoperation 1008.

Process 1000 is typically repeated as the measuring device and thescalar element are moving with respect to each other. In someembodiments, a plurality of images are captured as the measuring deviceand the scalar element are moving with respect to each other. Byprocessing multiple captured images, the absolute position can becalculated in real time as the measuring device and the scalar elementare moving with respect to each other.

As previously mentioned, in some cases, the absolute position isprovided to a motion control system as position feedback. In some casesthe absolute position is displayed to a user on, for example, a digitalread out display or a computer monitor display.

The measurement system 100 described with respect to FIG. 1 can set toproduce a position with respect to a home or reference position thatdoes not coincide with the end of the scalar element. For example, thesecond object 104 may be moved to one end of the range of travel. Aproximity switch or hard stop can be used to determine the home orreference location. The position of the second object 104 may be set tozero at this location. The absolute position may be determined using,for example, process 1000 described above. The difference between thereference position zero and the absolute position zero can be stored andadded (or subtracted) from subsequent measurements of absolute positionto determine a distance from the home or reference position.

The measurement system 100 described with respect to FIG. 1 can also becalibrated to provide a repeatable task or motion. For example, thesecond object may be attached to a piston used to deliver a quantity ofliquid. To calibrate the system, the second object may be moved to afirst position where the piston motion should begin. The second objectis then moved to a second position where the piston motion should end.The amount of liquid displaced or dispensed by the piston can bemeasured and the absolute positions of the first and second position canbe stored. A simple linear relationship can then be determined betweenabsolute position and the amount of liquid displaced or dispensed by thepiston.

A more detailed discussion of such a system is provided in a descriptionof a bottle dispenser embodiment that is attached as Appendices A and B.

FIG. 8 is an illustration of a caliper 800 modified using the positiondetection system of the subject invention. The caliper includes a pairof jaws 802 and 804. When the jaws are opened to obtain a measurement,the left jaw 802 remains stationary and the right jaw 804 moves thetight. This movement causes the position detection electronics housing806 to move to the right over stationary ruler 808. Ruler 808 includes ascalar element 810. As in the previous embodiments, the scalar elementwill include a series of coded regions. The scalar element can alsoinclude index marks.

Housing 806 includes a camera 812 aligned with the scalar element 810.As in the previous embodiments, in order to determine the spacing of thecaliper jaws, the camera obtains an image of the coded region. The codedregion provides information about the distance from the start or homeposition. Any of the various approaches for encoding of the coded regiondiscussed above can be used. For example, the coded regions can be inthe form of actual distances from the home position or can be a numberwhich is multiplied by a fixed distance.

In the illustrated embodiment, housing 806 includes a display 814 toshow the distance from the home position (jaws closed). A single switch816 is provided for turning on the electronics and for toggling betweeninches and millimeters in the display.

A ten bit binary encoding system would provide over 1000 unique binarycodes spaced apart at 0.1 mm to cover 100 mm caliper separation. Addingindex lines can double that range. Various approaches for printing thesetype of closely spaced codes can be used including lithographicprinting. As in the previous embodiments, the location of the codedregion within the two dimensional image generated by the camera can beused to provide position information with a higher resolution than thespacing between the coded regions.

It is envisioned that during the final manufacturing steps, the devicewill be subjected to a one time calibration procedure. Specifically, thejaws will be placed in the closed position and the aligned coded region(which is preferably spaced from the end of the scalar element) isdetected. The detected coded region will become the effective homeposition and will be uploaded to the software in the processor (notshown) in the housing. This value would then be subtracted from the anyvalue measured by the system when the jaws are separated.

What is claimed is:
 1. A measurement system for measuring the absoluteposition of a first object with respect to a second object along an axisof motion representing a direction of relative motion between the firstobject and the second object, the system comprising: a scalar elementattached to the first object, the scalar element comprising a series ofcoded regions positioned along an axis of the scalar element, whereinthe axis of the scalar element is parallel to the axis of motion,wherein: each coded region of the series of coded regions comprising arespective pattern of a series of patterns, each pattern of the seriesof patterns is located along a respective line perpendicular to the axisof motion, and variation of each of the respective patterns along therespective lines encodes information that represents a numberdesignating a position of the respective pattern along the axis of thescalar element; a measuring device attached to the second object, themeasuring device comprising a two-dimensional optical sensor arrayconfigured to capture an image of a portion of the scalar element, theimage comprising a first pattern in one coded region of the series ofcoded regions; and a processor configured to: receive the image; anddetermine an absolute position of the first object with respect to thesecond object based on the first pattern.
 2. The measurement system ofclaim 1, wherein each pattern of the series of patterns comprises abinary code that represents a respective number designating a respectiveposition along the axis of the scalar element.
 3. The measurement systemof claim 1, further comprising a display configured to display theabsolute position.
 4. The measurement system of claim 1, furthercomprising a motion controller configured to receive the absoluteposition, and to cause a movement of the first object along the axis ofmotion based on the received absolute position.
 5. The measurementsystem of claim 1, wherein the measuring device is configured to capturea plurality of images as the first or second object move along the axisof motion, and the processor is configured to determine, in real time, arespective absolute position for each of the plurality of images.
 6. Themeasurement system of claim 1, wherein: each coded region of the seriesof coded regions comprises a respective colored region, and theprocessor is further configured to determine the absolute position ofthe first object with respect to the second object based on a firstcolored region included in the one coded region comprising the firstpattern.
 7. The measurement system of claim 1, wherein: each codedregion of the series of coded regions comprises a respective pluralityof colored regions, and the processor is further configured to determinethe absolute position of the first object with respect to the secondobject based on a first plurality of colored regions included in onecoded region comprising the first pattern.
 8. The measurement system ofclaim 1, wherein the two-dimensional optical sensor array is a camerasensor.
 9. The measurement system of claim 1, wherein the scalar elementattached to the first object further comprises a series of regularlyrepeating optically readable index lines positioned along the axis ofthe scalar element.
 10. The measurement system of claim 9, wherein theimage of the portion of the scalar element comprises a first index line,a first coded region, and an additional feature that is either a secondindex line or a second coded region.
 11. A method of determiningabsolute position of a first object with respect to a second objectalong an axis of motion representing a direction of relative motionbetween the first object and the second object, the method comprising:acquiring an image of a portion of a scalar element attached to thefirst object using a measuring device attached to the second object,wherein: the scalar element comprises a series of coded regionspositioned along an axis of the scalar element, wherein the axis of thescalar element is parallel to the axis of motion, each coded region ofthe series of coded regions comprising a respective pattern of a seriesof patterns, each pattern of the series of patterns is located along arespective line perpendicular to the axis of motion, variation of eachof the respective patterns along the respective lines encodesinformation that represents a number designating a position of therespective pattern along the axis of the scalar element; and themeasuring device comprises a two-dimensional optical sensor arrayconfigured to capture an image of a portion of the scalar element, theimage comprising a first pattern in one coded region of the series ofcoded regions; performing image processing on the acquired image toobtain a representation of the one coded region; determining a numbervalue represented by the representation of the one coded region, whereinthe number value defines the absolute position of the first patternalong the axis of the scalar element based on the information encoded bythe first pattern; determining the absolute position of the first objectwith respect to the second object along the scalar element based on thenumber value.
 12. The method of claim 11, further comprising displayingthe absolute position on a display.